Re: [PATCH 2/7] udp_vu: Assert iov_tail_clone() return before assigning to msg_iovlen

[David Gibson <david@gibson.dropbear.id.au>]

[-- Attachment #1: Type: text/plain, Size: 1442 bytes --]

On Wed, Jul 08, 2026 at 06:31:58PM -0400, Jon Maloy wrote:
> iov_tail_clone() returns ssize_t, but its return value was assigned
> directly to msg.msg_iovlen which is size_t. Add an assert to document
> the invariant that the clone into a VIRTQUEUE_MAX_SIZE array cannot

Nit: I think s/invariant/assumption/ would be clearer.

> fail.
> 
> Signed-off-by: Jon Maloy <jmaloy@redhat.com>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

> ---
>  udp_vu.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/udp_vu.c b/udp_vu.c
> index e4fb1057..5d6f45ec 100644
> --- a/udp_vu.c
> +++ b/udp_vu.c
> @@ -67,11 +67,14 @@ static ssize_t udp_vu_sock_recv(struct iov_tail *payload, size_t *cnt, int s)
>  	struct iovec msg_iov[VIRTQUEUE_MAX_SIZE];
>  	struct msghdr msg  = { 0 };
>  	size_t iov_used;
> +	ssize_t iovlen;
>  	ssize_t dlen;
>  
> +	iovlen = iov_tail_clone(msg_iov, ARRAY_SIZE(msg_iov), payload);
> +	assert(iovlen >= 0);
> +
>  	msg.msg_iov = msg_iov;
> -	msg.msg_iovlen = iov_tail_clone(msg.msg_iov, ARRAY_SIZE(msg_iov),
> -					payload);
> +	msg.msg_iovlen = iovlen;
>  
>  	/* read data from the socket */
>  	dlen = recvmsg(s, &msg, 0);
> -- 
> 2.52.0
> 

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]